package repository links

[Colin Macdonald]

Hi all,

The URLs in the DESCRIPTION files of doctest and symbolic now point to 
their https://octave.sourceforge.io/*/ sites.  This is the right thing 
b/c those are the official sites.

But these two packages are (currently) developed on largely github.com.

The generate_html package makes links to the repository of the form
https://octave.sourceforge.io/pkg-repository/doctest/
but these are a bit misleading for (at least) these two packages.

Options:

1. hack the generated html "manually" (probably some sed in the 
maintainer makefile).

2. add a new "dev_url", "repo", "dev_repo", or similar field to DESCRIPTION.

3. something else I haven't thought of.

The first option is nice and easy, but a bit "local"...  Thoughts?

Colin